Strobist - Know Your Sync

[KevinBarrett]

I just read an interesting article on Strobist about knowing your camera's sync speed. Apparently some manufactures fudge a little bit about cameras' true flash sync speeds. For instance, an EOS 5D MkII's advertised sync speed is 1/200 of a second, while many have found they must go down to 1/160 to get their whole frame properly exposed when using flash. A Sony a700, on the other hand, has an advertised sync speed of 1/250 or 1/200 with SSS turned on, while I've had little trouble lighting images with SSS turned on at 1/250.

Does anybody have any experience or input about the true sync speeds of their Alpha cameras?

http://strobist.blogspot.com/2010/01/kn ... -sync.html

[harvey]

...A Sony a700, on the other hand, has an advertised sync speed of 1/250 or 1/200 with SSS turned on, while I've had little trouble lighting images with SSS turned on at 1/250.

Does anybody have any experience or input about the true sync speeds of their Alpha cameras?

http://strobist.blogspot.com/2010/01/kn ... -sync.html

I have been using 1/250s with the A900 and skyport-fired flash. I quite often forget to turn off SSS,
even when using a tripod but I have not noticed any problem with 1/250s and SSS.

Harvey

[Greg Beetham]

Apart from the 'figures' given in the camera manuals for flash sync speed (good sensible figures btw that should be taken notice of), there are circumstances that could give the impression of being able to exceed the set figures. The big variable is, how much influence did daylight or local ambient play in the shot? along with ISO and f-stop of course...and the response/timing/output of the particular strobe/flash's. If the ambient conditions is such that there is quite a lot of light in the shot apart from the flash contribution then you might get away with exceeding the sync speed and not notice anything.
Otoh if you were to have a fast flash response time (relatively fast f-stop) in a fairly low ambient situation with a high iso and a shutter speed exceeding the sync speed you most likely will see a band in the photo.
I just experimented on my KM5D with this and it is indeed so, I got it to fire in S mode at 1/250 sec with the HS3600 (D) at f3.5 and ISO400 (only a reading lamp illuminating part of the room, the rest in semi darkness), and I got a nice black band accross the bottom of the photo. It would only let me do it to it the once though, from then on I could not exceed 1/125 sec in S mode or M mode with the flash turned on, (AS turned on also).
To do another I'd have to set up the A700 and utilize the sync socket with an old Metz, unless I can trick the A100....hmm
Both the KM5D and the A100 have 1/125 sec sync with the Anti Shake system turned on, and 1/160 sec with it turned off. The A700 has 1/200 sec (SSS on) and 1/250 sec (SSS off). I might try some experiments on it later.
Both the KM5D and the A100 have a minimum shutter cycle time of 1/160 sec. (with the shutter fully open), the A700 has a minimum shutter cycle time of 1/250 sec (shutter fully oipen), even at the 'fastest' shutter speed possible the cycle times don't get any faster, the slit just gets narrower progressively after you go past the sync speed.
By exceeding the recommended sync speed you do run the risk of loosing a once in a long time shot....(just a thought).
Greg